So, I am not sure what I can do...
A direct email from RCCL indicates you can only bring on non-alcoholic drinks "in-hand" as there are plenty of drink choices on board.

On the other hand, I have heard folks just putting a luggage tag on their case of water or soda and they check that in. Putting it in a suitcase is not an option, as we are doing a 12 day cruise + 2 women + formal nights + + pool outfits + dancing outfits + shoes = no room in a suitcase for a case of drinks! lol

My partner and I drink and prefer flavored water, and we were hoping to bring a case on board, (we are taking a car service to the pier) and check it in with our luggage.